1. Field of Invention
This invention is directed to a method and apparatus for detecting failures in the blower and ventilation circuits in the ventilation system of a large electric power generator, and more particularly, to such a method and apparatus which detect such failures reliably from differential pressure measurements regardless of the purity or density of the cooling gas.
2. Background Information
Large electric generators are cooled with pressurized hydrogen and have an internal ventilation system which uses a blower to continuously circulate the gas through a gas cooler, and about the components to be cooled. This internal ventilating system's integrity must be maintained during operation to properly cool the generator. Blower failure, baffle failure and improper assembly have caused malfunctions in such ventilating systems.
During operation, the internal parts of the generator cannot be visually inspected, and hence the internal ventilation system is monitored by temperature measurements, and by measurements of the differential pressure across the generator blower, that is the difference between the inlet and outlet pressure of the blower. Monitoring of the temperature of course indicates when a portion of the unit is getting too hot. And monitoring of the generator blower differential pressure can indicate power failure. However, the present method is not completely satisfactory for monitoring the ventilating system because changes in blower pressure and the temperatures are not easily correlated with ventilation system failures. The blower pressure depends upon gas purity, pressure, and temperature which are not constant and make monitoring by measuring the blower pressure and temperatures impractical. Also, the temperatures in the circuits of the ventilation system are not measured at every point, and often only average temperatures are measured which may not reflect local changes in the ventilation circuits.
It is normal practice to monitor the purity of the ventilating system gas to detect any ingress of impurities into the generator gas. It is common to determine gas purity by monitoring the differential pressure across a constant displacement purity blower which extracts a stream of gas from the ventilating system and discharges it back into the system. It has been known to use the differential pressure across the generator blower as a back up means for determining gas purity. However, no reliable system for detecting failures in the ventilation using pressure measurements has been available.
In the meantime, major failures of the generator have occurred because damage or changes to the ventilation system during operation were not detected.
It is therefore a primary object of the invention to provide a reliable; simple system for detecting failures in the ventilation system of large gas cooled electric generator before major damage occurs.
It is a more particular object of the invention to provide such a system which utilizes pressure measurements in the ventilation system.
It is another particular object of the invention to provide such a system that takes advantage of equipment already available in the generator unit.